1. Field of the Invention
The present invention is related to a control method for improving luminous uniformity of a display device, and the related luminosity calibrating controller and display device, and more particularly, to a control method which can utilize a small number of gamma tables to improve the luminous uniformity of the entire pixels, and the related luminosity calibrating controller and display device.
2. Description of the Prior Art
As the video display technology advances, consumers kept asking for even higher quality of display device. In general, there are several aspects to judge the quality of a display device; for example, a good display device has to be highly stable and reliable, and the picture displayed should be of good quality. To improve the quality of the picture, the display device should have higher resolution and can display good color, and the luminosity of the displayed images must be uniform. Taking the LCD device as an example, because the luminosity distribution of the LCD backlight is not perfect, and also the driving voltages and the liquid crystal characteristics of the different pixels may present certain differences, such that the LCD device cannot have good luminous uniformity, and some calibrating method is required to achieve luminous uniformity. Considering the viewpoint of an ordinary consumer, and let the consumer to observe an image of the same gray level, and the image is displayed by a LCD device without applying any luminosity calibration, then he/she is likely to find that different areas on the display device may present very different luminosity for the image data of same gray level. On the other hand, if a fine luminosity meter is applied to measure the displayed image of same gray level, then it can be found that different pixels may read out different luminous value, and the difference can be large. Usually, by comparing the luminous values in the central part and the boundary part of the displayed image, an obvious difference in luminosity can be observed. Under this condition, in order to make the luminosity more uniform, a proprietary circuit for luminosity calibration must be built in the display device, and a strict luminous calibration procedure must be applied in the production process of the display device. After the calibration process is done in the manufacturing process, the display device can perform the luminosity calibration (or called luminosity compensation) to the input image data, while operating in the normal mode, such that the displayed images are of good luminous uniformity, and the display device can be qualified as a high quality display device.
The objective of the luminosity calibration is to make any two pixels of the display device to display the same luminous value for the same gray level of image data. For various reasons, like those stated above, any two pixels of a display device without doing a luminosity calibration are unlikely to display the same luminous value for the same gray level. To improve the luminous uniformity, a luminosity calibration procedure is thus required. The method of luminosity calibration is to adjust the input gray level of the image data to produce a new gray level, such that the displayed luminosity is as close as possible for the same input gray level. And, the difference between the new gray level and the original input gray level is called the luminosity calibrating value δE. In general, since the number of pixels in the display device is enormously large, a pixel-by-pixel luminosity calibration process will take vast amount of time, and it will take hours or even tens of hours to complete the calibration process for only a display device, such that the cost is high. Meanwhile, after completing the luminosity calibration, the display device must include a memory device to store the calibrating value δE for the entire gray levels of every pixel, thus a large memory space is required in the circuit, and sometimes needs an external dynamic RAM (DRAM) to store all the calibrating values.